There are lots of different types of worms that like to live in dogs. Some of them are annoying but not dangerous, but one can be deadly. Most puppies have roundworms at some point in their lives. Worming your new puppy is generally part of its first visit to the vet. The other types of worms that dogs get: hookworms, tapeworms, and whipworms, are easily treatable. The most dangerous kind of worm that affects dogs is the heartworm. This is spread by mosquitoes and can be fatal if not treated. Make a heartworm check a regular part of your dog's annual vaccination. There are medicines available to prevent your dog from becoming infected. If evidence of heartworms is found, they can be controlled, but your dog will have to be on medication for the rest of its life.